where \(\bar{F}(x(t), \lambda (t))= \int ^t_0 dt^{\prime } F(x(t^{\prime }),\lambda (t^{\prime }))\) ,
\(x_0=x(0)\) , and we have used Eq. (REF ) relating
\(\xi ^{H}_{fGn}\)  to \(\xi ^H_{fBm}\) . Equation (REF ) can be
formally solved in terms of the Riemann-Liouville fractional
differential operator \({}_0 D^{\beta }_t\) 
[1]}, [2]}, yielding
\({}_0 D^{(H+\frac{1}{2})}_t \left({x}(t)-x_0\right) - \mu \, {}_0 D^{(H+\frac{1}{2})}_t \bar{F}(x(t), \lambda (t))= \xi (t).\) 
